Wave augmented diffuser for centrifugal compressor

Abstract

A wave augmented diffuser for a centrifugal compressor surrounds the outlet of an impeller that rotates on a drive shaft having an axis of rotation. The impeller brings flow in in an axial direction and imparts kinetic energy to the flow discharging it in radial and tangential directions. The flow is discharged into a plurality of circumferentially disposed wave chambers. The wave chambers are periodically opened and closed by a rotary valve such that the flow through the diffuser is unsteady. The valve includes a plurality of valve openings that are periodically brought into and out of fluid communication with the wave chambers. When the wave chambers are closed, a reflected compression wave moves upstream towards the diffuser bringing the flow into the wave chamber to rest. This action recovers the kinetic energy from the flow and limits any boundary layer growth. The flow is then discharged in an axial direction through an opening in the valve plate when the valve plate is rotated to an open position. The diffuser thus efficiently raises the static pressure of the fluid and discharges an axially directed flow at a radius that is predominantly below the maximum radius of the diffuser.

What is claimed is:  
     
       1. A diffuser for use with an impeller having an inlet and an outlet, the diffuser comprising: 
       a plurality of vanes disposed at the outlet of the impeller;  
       a wave chamber disposed between adjacent vanes, each wave chamber having an inlet and an outlet; and  
       a valve plate having at least one valve opening; the valve opening selectively opening and closing the outlet of at least one wave chamber.  
     
     
       2. The diffuser of claim  1 , wherein the valve plate rotates with respect to the wave chambers. 
     
     
       3. The diffuser of claim  2 , further comprising a drive shaft; the valve plate mounted on the drive shaft with the impeller adapted to be mounted on the drive shaft such that the valve plate and impeller rotate together. 
     
     
       4. The diffuser of claim  1 , wherein the valve plate includes one valve opening for every two wave chambers. 
     
     
       5. The diffuser of claim  1 , wherein each valve opening includes an outer portion and an inner portion. 
     
     
       6. The diffuser of claim  5 , wherein each outer portion of the valve opening is offset from the inner portion of the valve opening. 
     
     
       7. The diffuser of claim  6 , wherein the outer portion and inner portion of each valve opening are connected to form a single opening. 
     
     
       8. The diffuser of claim  6 , wherein the outer portion and inner portion of each valve opening are separated from each other to form two individual openings. 
     
     
       9. A diffuser for use with an impeller having an inlet and an outlet, the impeller rotating about an axis of rotation, the inlet to the impeller accepting a fluid flow substantially parallel to the axis of rotation, the fluid flow passing through the outlet in a direction substantially perpendicular to the axis of rotation; the diffuser comprising: 
       a plurality of vanes disposed at the outlet of the impeller;  
       a wave chamber disposed between adjacent vanes, each wave chamber having a maximum outer radius;  
       each wave chamber having an inlet aligned with the outlet to the impeller;  
       each wave chamber further having an outlet substantially perpendicular to the inlet of the wave chamber; the outlet having a maximum outer radius;  
       the maximum radius of the outlet being no greater than the maximum outer radius of the wave chamber; and  
       a valve selectively opening and closing the outlet to the wave chamber.  
     
     
       10. The diffuser of claim  9 , wherein the valve is a valve plate having at least one valve opening; the valve plate rotating with respect to the wave chamber. 
     
     
       11. A method of diffusing a fluid flow in a centrifugal compressor, comprising the steps of: 
       delivering a fluid flow to the input of the impeller of the diffuser, the fluid flow traveling in an input direction axial to the impeller;  
       imparting kinetic energy to a fluid flow with the impeller;  
       turning the fluid flow with the impeller from the axial direction to a radial outlet direction substantially perpendicular to the input direction;  
       delivering the fluid flow from the impeller to a plurality of wave chambers, each of the wave chambers having a maximum outer radius; and wherein each wave chamber has an outlet;  
       providing a valve in communication with the outlet to each wave chamber and opening and closing the outlet of each wave chamber with the valve;  
       stalling the fluid flow in the wave chamber;  
       redirecting the fluid flow from the radial outlet direction to an axial direction within the wave chamber inside the maximum outer radius of the wave chamber.  
     
     
       12. The method of claim  11 , further comprising the step of increasing the pressure of the fluid flow while the step of stalling the fluid flow occurs. 
     
     
       13. A method of diffusing a fluid flow delivered from the outlet of an impeller in a radial and tangential direction, the impeller rotating about an axis of rotation; the method comprising the steps of: 
       delivering the fluid flow from the outlet of the impeller to a plurality of wave chambers, each of the wave chambers having an inlet and an outlet; and  
       selectively opening and closing the outlets of the wave chambers.  
     
     
       14. The method of claim  13 , further comprising the step of creating a compression wave in the fluid in a wave chamber when the outlet of the wave chamber is closed. 
     
     
       15. The method of claim  13 , further comprising the step of creating an expansion fan in the fluid in a wave chamber when the outlet of the wave chamber is open.